This application claims the priority of German Application No. 10 2005 027 193.6, filed Jun. 6, 2005, the disclosure of which is expressly incorporated by reference herein.
The present invention relates to a twin unit including two drafting devices for drafting fiber strands for a spinning machine. One housing is provided for both of the drafting devices, which housing is mounted in a detachable way on a machine frame. Each of the drafting devices can be driven separately, whereby the drafting devices are arranged essentially mirror-symmetrical to one another and include a number of drivable bottom rollers, and whereby each bottom roller includes an area which drafts the fiber strand.
A spinning machine built in modular design is known in European published patent application 1 422 323. A number of self-supporting spinning units attached to a machine frame are provided there in machine longitudinal direction, which units serve the production of yarn. Each spinning unit can, as a module, be simply replaced. In the case of airjet spinning machines, these spinning units include at least one drafting device, a drive and an airjet assembly. The drafting device of each individual spinning position can be separately driven.
In the case of drafting devices of this type which are driven separately, it is standard practice to support the bottom rollers in an overhung position. The bottom rollers are hereby supported only on their ends facing the housing, while the area of the bottom roller which drafts the fiber strand projects upwards from the frame and has there no further bearing point.
For reasons of efficient use of space it is intended that, in the spinning machine, the smallest possible gauge, that is the smallest possible distance between each spinning position, is realized. The spinning units having a complete housing for each individual drafting device and the overhung supported bottom rollers therein have the disadvantage in that they set limits to the reduction of the gauge.
The overhung supporting arrangements have the disadvantage in that they require a very complicated bearing of large dimensions. The shorter the bearing is designed, the higher the bearing forces are.
From the German published patent application 39 04 348 it is known that such drafting devices having overhung supported bottom rollers are designed as twin units, in which two drafting devices are arranged in a common housing. Both drafting devices are arranged essentially mirror-symmetric to one another and are driven separately. Due to the mirror-symmetrical assembly as a twin unit, a little saving of space can be achieved, but because of the overhung supported bottom rollers, quite a large installation space is still required.
There is therefore needed a spinning unit in which the space requirements in a longitudinal direction of the spinning machine are reduced, thus permitting a smaller gauge.
These needs are achieved in that each bottom roller includes two bearing points, whereby one bearing point is arranged on each side of the area which drafts the fiber strand.
By placing two bearing points essentially at both ends of the bottom rollers, the bearing forces are reduced and the bearing points can be of smaller dimensions. The support of the bottom roller on both sides of the area which drafts the fiber strand avoids a multiplication of the forces mainly occurring due to the pressure of the assigned top rollers, as such multiplication occurs in the case of the overhung support. Rather, the load is divided almost evenly between both bearing points.
Due to the mirror-symmetric arrangement, both bottom rollers, which lie opposite one another on either side of the plane of symmetry of the twin unit, may be defined as a bottom roller pair. These bottom roller pairs of both drafting devices of the twin unit are often only jointly adjusted in their position along the fiber transport direction. It is then advantageous when the bearing points facing the plane of symmetry include a joint bearing take-up. Design and adjustability are hereby simplified, and further installation space can be saved by placing the bearing points accordingly.
Flexibly pressable top rollers are arranged with respect to the bottom rollers of the drafting device. The top rollers can be supported and pressed in different ways. If it is necessary that individual top rollers be raised separately, then these top rollers are advantageously individually supported and pressed. In order to further reduce space requirements, it may be advantageous to design as many top rollers as so-called twin pressure rollers. The two top rollers of a so-called bottom roller pair are hereby rotatably supported on a joint stationary axle and pressed by a joint loading assembly.
It is in addition advantageous to assign to each drafting device at least one separate drive motor, which is also arranged in the housing of the twin unit. Thus, each drafting device can be individually controlled and also brought to standstill in a simple way.
These and further objects, features and advantages of the present invention will become more readily apparent from the following detailed description thereof when taken in conjunction with the accompanying drawings wherein.